A powerful storm with hurricane-force winds raked across the Northeast on Sunday and into Monday morning, knocking out power to more than a million homes and businesses.

The storm, which dumped several inches of rain in areas stretching from New Jersey to Maine, uprooted trees and brought down branches throughout the region. Tumbling trees knocked over power lines and poles, and utility providers warned that restoring electricity could take several days.

The hardest-hit state appeared to be Maine, where 461,000 customers were without electricity as of noon Monday. The state’s governor, Paul R. LePage, declared a state of emergency that was intended to help utility companies restore power more quickly.

A spokeswoman for the Central Maine Power Company, which had 365,000 customers without power as of 8 p.m. Monday, said repair crews were working to ground live wires that had been knocked down. “We won’t have a restoration estimate until tomorrow at the earliest and possibly later than that,” the spokeswoman, Gail N. Rice, said in an email.

National Grid said it was using helicopters to survey damage to its power lines in Massachusetts and Rhode Island. “Customers should be prepared that restoration could be a multiday effort due to the extensive damage,” the company said in a statement.

The storm dropped more than three inches of rain in Central Park in Manhattan, according to the National Weather Service, and more than five inches in western parts of Connecticut and Massachusetts and in southern Vermont. The strongest winds pummeled the coastal areas, including a gust of 83 miles per hour recorded on Cape Cod in Massachusetts.

But the most powerful gust recorded was 130 m.p.h. on Mount Washington in New Hampshire, the highest point in New England, the Weather Service said. As of Monday night, a spokesman for the state’s Department of Safety said 180,000 customers were without power.

About 219,000 customers were without power in Massachusetts at 8 p.m. Monday, according to the state’s Emergency Management Agency. At that time, 102,000 customers were still without power in Connecticut, according to the utility company Eversource Energy.

A collision of warm air from the south and cooler air from Canada helped fuel the storm, which struck five years after Hurricane Sandy.